stages: add test stage

Adds a new systemd unit to the image that will be pulled in by default,
run a given command, forward the output to a virtio serial port and
shutdown the machine.

We add a sample that uses this to verify that systemd conciders the
machine successfully booted. A simple way to run this test from the
commandline is to use
  `$ socat UNIX-LISTEN:qemu.sock -`
to listen for either `running` for success or `degraded` or
`maintenance` for failure.

The image should then be booted using something like
  `$ qemu-kvm -m 1024 -nographic -monitor none -serial none -chardev socket,path=qemu.sock,id=char0 -device virtio-serial -device virtserialport,chardev=char0,id=test0 -snapshot  base.qcow2`

Signed-off-by: Tom Gundersen <teg@jklm.no>

samples/base-qcow2.json

@@ -53,12 +53,6 @@
         "kernel_opts": "ro biosdevname=0 net.ifnames=0"
       }
     },
-    {
-      "name": "org.osbuild.debug-shell",
-      "options": {
-        "tty": "/dev/ttyS0"
-      }
-    },
     {
       "name": "org.osbuild.selinux",
       "options": {

samples/base-test.json

@@ -0,0 +1,80 @@
+{
+  "name": "base-qcow2",
+  "stages": [
+    {
+      "name": "org.osbuild.dnf",
+      "options": {
+        "releasever": "30",
+        "install_weak_deps": true,
+        "repos": {
+          "fedora": {
+            "name": "Fedora",
+            "metalink": "https://mirrors.fedoraproject.org/metalink?repo=fedora-$releasever&arch=$basearch",
+            "gpgkey": "file:///etc/pki/rpm-gpg/RPM-GPG-KEY-fedora-$releasever-$basearch"
+          }
+        },
+        "packages": [
+          "@Core",
+          "chrony",
+          "kernel",
+          "selinux-policy-targeted",
+          "grub2-pc",
+          "spice-vdagent",
+          "qemu-guest-agent",
+          "xen-libs",
+          "langpacks-en"
+        ]
+      }
+    },
+    {
+      "name": "org.osbuild.locale",
+      "options": {
+        "language": "en_US"
+      }
+    },
+    {
+      "name": "org.osbuild.fstab",
+      "options": {
+        "filesystems": [
+          {
+            "uuid": "76a22bf4-f153-4541-b6c7-0332c0dfaeac",
+            "vfs_type": "ext4",
+            "path": "/",
+            "freq": "1",
+            "passno": "1"
+          }
+        ]
+      }
+    },
+    {
+      "name": "org.osbuild.grub2",
+      "options": {
+        "root_fs_uuid": "76a22bf4-f153-4541-b6c7-0332c0dfaeac",
+        "kernel_opts": "ro biosdevname=0 net.ifnames=0"
+      }
+    },
+    {
+      "name": "org.osbuild.test",
+      "options": {
+        "script": "/usr/bin/systemctl is-system-running --wait"
+      }
+    },
+    {
+      "name": "org.osbuild.selinux",
+      "options": {
+        "file_contexts": "etc/selinux/targeted/contexts/files/file_contexts"
+      }
+    },
+    {
+      "name": "org.osbuild.fix-bls"
+    }
+  ],
+  "assembler":
+    {
+      "name": "org.osbuild.qcow2",
+      "options": {
+	"filename": "base.qcow2",
+        "root_fs_uuid": "76a22bf4-f153-4541-b6c7-0332c0dfaeac"
+      }
+    }
+}